[MITgcm-support] Relaxation constant for salinity, tauSaltClimRelax in Global Ocean Simulation at 4deg resolution.

[David Ferreira]

  Hi Krishnakumar,
> My question is regarding the relaxation constant for salinity in the 
> tutorial (tutorial_global_oce_latlon). In the case of potential 
> temperature, we calculated the tauThetaClimRelax according to the 
> publication by Barnier et. al (Barnier et. al : Thermal forcing for a 
> global ocean circulation model using a three-year climatology of ECMWF 
> analyses, Journal of Marine Systems, 1995.) and are getting values in 
> the range of 60days, which is also the value chosen in tutorial.
> For salinity, however, I am unable to get hold of any 
> reference/publication which discusses in detail the calculation of 
> tauSaltClimRelax. Please let me know how this quantity 
> (tauSaltClimRelax) could be calculated.
There is no physical justification to tauSaltClimRelax. The non-physical 
justification is that it "works", i.e it keeps the solution close to S* 
(usually some observed climatology).
>
> Finally, I feel that the net fresh water surface flux, EmPmR, would 
> depend primarily on temperature than on salinity. If true, the 
> relaxation term in the salinity equation could look like,
>
> dS/dt= (1/tauSaltClimRelax)*(theta - theta*) + flux (T*,S*)
This looks very strange. It doesn't have the right dimension. Also, even 
if evaporation could be approximated as a function of SST, it is less 
clear for precipitation.
> rather than
>
> dS/dt=(1/tauSaltClimRelax)*(S-S*) + flux(S*)
>
> But then, I am not sure whether the salinity solution would converge 
> to S*. And of course the determination of tauSaltClimRelax would still 
> require some reference.
>
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